Pedro Ciriaco will start his first game as a Padre Saturday night as left fielder Carlos Quentin was a late scratch with a sore left shoulder.

“He maybe did it on a swing late in the game,” Padres manager Bud Black explained after scratching Quentin from the starting lineup.

Logan Forsythe will make his professional debut as an outfielder in left Saturday night. He will hit in the fifth slot behind Kyle Blanks.

And Ciriaco, who the Padres acquired from the Boston Red Sox Friday in exchange for a player to be named later, will start at second and bat eighth in his Padres debut. Ciriaco was hitting .216 for the Red Sox.

The Padres Saturday night (7:10 p.m.) will be looking to win a fifth straight game for the first time this season in the middle game of a three-game series against the National League West-leading Arizona Diamondbacks.

A fifth straight win would also get the Padres to .500 for the first time this season. They were 5-15 on April 23.

The Padres have had three, four-game winning streaks.

In other news Saturday, the Dodgers claimed catcher John Baker off waivers from the Padres and immediately optioned him to Triple-A Albuquerque.

Baker, who was optioned to Triple-A Tucson on May 28 when Yasmani Grandal finished serving his 50-game suspension (tested positive last September for the performance-enhancing drug testosterone). Baker was designated for assignment last Monday when Forsythe was moved onto the 40-man roster from the 60-day disabled list.

Baker, 32, made 64 starts for the Padres at catcher over the last two seasons. He hit .223 with no homers and 16 RBIs in 233 at-bats.

DIAMONDBACKS (37-30) at PADRES (33-34)

Time: 7:10 p.m. Game: 2 of 3

TV: Fox Sports San Diego

Radio: 1090-AM, 860-AM (Spanish)

Today’s matchup

Diamondbacks LHP Wade Miley (4-5, 4.89 ERA)

Miley vs. the Padres: 1-4 career, 7.52 ERA in six games (0-2 this season, 11.88 ERA in two starts).

Miley at Petco Park: 1-3 career, 5.70 ERA in four starts (0-1 this season, 7.20 ERA in one start).

Although the Diamondbacks have won the last two games started by the 26-year-old Miley, he is 1-3 with a 6.75 ERA over his last five starts. Nine of his first 13 starts this season have come on the road.

Marquis is 2-0 over his last two starts, allowing four runs on eight hits over 14 innings. He has won seven straight decisions, matching the second-longest streak in the National League this season. He is 7-0 and the Padres are 8-1 over his last nine starts. He has a 3.17 ERA over the nine games.